| Structural highlights
Function
[BRI1_ARATH] Receptor with a dual specificity kinase activity acting on both serine/threonine- and tyrosine-containing substrates. Regulates, in response to brassinosteroid binding, a signaling cascade involved in plant development, including expression of light- and stress-regulated genes, promotion of cell elongation, normal leaf and chloroplast senescence, and flowering. Binds brassinolide, and less effectively castasterone, but not 2,3,22,23-O-tetramethylbrassinolide or ecdysone. May be involved in a feedback regulation of brassinosteroid biosynthesis. Phosphorylates BRI1-associated receptor kinase 1 (BAK1), Transthyretin-Like protein (TTL) and SERK1 on 'Ser-299' and 'Thr-462' in vitro. May have a guanylyl cyclase activity.[1] [2] [3] [4] [5] [6]
Publication Abstract from PubMed
Brassinosteroids, which control plant growth and development, are sensed by the membrane receptor kinase BRASSINOSTEROID INSENSITIVE 1 (BRI1). Brassinosteroid binding to the BRI1 leucine-rich repeat (LRR) domain induces heteromerisation with a SOMATIC EMBRYOGENESIS RECEPTOR KINASE (SERK)-family co-receptor. This allows the cytoplasmic kinase domains of BRI1 and SERK to interact, transphosphorylate and activate each other. Here we report crystal structures of the BRI1 kinase domain in its activated form and in complex with nucleotides. BRI1 has structural features reminiscent of both serine/threonine and tyrosine kinases, providing insight into the evolution of dual-specificity kinases in plants. Phosphorylation of Thr1039, Ser1042 and Ser1044 causes formation of a catalytically competent activation loop. Mapping previously identified serine/threonine and tyrosine phosphorylation sites onto the structure, we analyse their contribution to brassinosteroid signalling. The location of known genetic missense alleles provide detailed insight into the BRI1 kinase mechanism, while our analyses are inconsistent with a previously reported guanylate cyclase activity. We identify a protein interaction surface on the C-terminal lobe of the kinase and demonstrate that the isolated BRI1, SERK2 and SERK3 cytoplasmic segments form homodimers in solution and have a weak tendency to heteromerise. We propose a model in which heterodimerisation of the BRI1 and SERK ectodomains brings their cytoplasmic kinase domains in a catalytically competent arrangement, an interaction that can be modulated by the BRI1 inhibitor protein BKI1. This article is protected by copyright. All rights reserved.
Crystal structures of the phosphorylated BRI1 kinase domain and implications for brassinosteroid signal initiation.,Bojar D, Martinez J, Santiago J, Rybin V, Bayliss R, Hothorn M Plant J. 2014 Jan 26. doi: 10.1111/tpj.12445. PMID:24461462[7]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Noguchi T, Fujioka S, Choe S, Takatsuto S, Yoshida S, Yuan H, Feldmann KA, Tax FE. Brassinosteroid-insensitive dwarf mutants of Arabidopsis accumulate brassinosteroids. Plant Physiol. 1999 Nov;121(3):743-52. PMID:10557222
- ↑ Friedrichsen DM, Joazeiro CA, Li J, Hunter T, Chory J. Brassinosteroid-insensitive-1 is a ubiquitously expressed leucine-rich repeat receptor serine/threonine kinase. Plant Physiol. 2000 Aug;123(4):1247-56. PMID:10938344
- ↑ Belkhadir Y, Chory J. Brassinosteroid signaling: a paradigm for steroid hormone signaling from the cell surface. Science. 2006 Dec 1;314(5804):1410-1. PMID:17138891 doi:https://dx.doi.org/10.1126/science.1134040
- ↑ Kwezi L, Meier S, Mungur L, Ruzvidzo O, Irving H, Gehring C. The Arabidopsis thaliana brassinosteroid receptor (AtBRI1) contains a domain that functions as a guanylyl cyclase in vitro. PLoS One. 2007 May 23;2(5):e449. PMID:17520012 doi:https://dx.doi.org/10.1371/journal.pone.0000449
- ↑ Wang X, Kota U, He K, Blackburn K, Li J, Goshe MB, Huber SC, Clouse SD. Sequential transphosphorylation of the BRI1/BAK1 receptor kinase complex impacts early events in brassinosteroid signaling. Dev Cell. 2008 Aug;15(2):220-35. doi: 10.1016/j.devcel.2008.06.011. PMID:18694562 doi:10.1016/j.devcel.2008.06.011
- ↑ Oh MH, Wang X, Kota U, Goshe MB, Clouse SD, Huber SC. Tyrosine phosphorylation of the BRI1 receptor kinase emerges as a component of brassinosteroid signaling in Arabidopsis. Proc Natl Acad Sci U S A. 2009 Jan 13;106(2):658-63. Epub 2009 Jan 5. PMID:19124768 doi:0810249106
- ↑ Bojar D, Martinez J, Santiago J, Rybin V, Bayliss R, Hothorn M. Crystal structures of the phosphorylated BRI1 kinase domain and implications for brassinosteroid signal initiation. Plant J. 2014 Jan 26. doi: 10.1111/tpj.12445. PMID:24461462 doi:https://dx.doi.org/10.1111/tpj.12445
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